In the prior art, various ester compounds are known as an oily base used in cosmetics.
DEOS 19724626 discloses a sunscreen composition comprising a specific ultra-violet ray absorber of a triazine type and triglycerin dimerate isostearate. The ester compound is used as an emulsifier in W/O emulsion.
However, the ester compound is poor in compatibility with oily bases. Further it was difficult to obtain an ester compound in a homogeneous state in a reproducible manner because highly viscous substances formed in the condensation of triglycerin, which is a hexavalent alcohol, with isostearic acid and dimer acid.
Japanese Patent Application Laid-Open 2002-275020 discloses an oily base comprising an ester of at least one alcohol selected from the group consisting of divalent alcohols having 4 to 22 carbon atoms and tri- or higher-valent alcohols having 3 to 22 carbon atoms with one or two acids selected from the group consisting of dimer acids and hydrogenated dimer acids. As examples of the ester of divalent alcohols having 4 to 22 carbon atoms with dimer acid, mention is made of an ester compound of decane diol with dimer acid. As examples of the ester of tri- or higher-valent alcohols having 3 to 22 carbon atoms with dimer acid, mention is made of an ester compound of glycerin with dimer acid.
However, polymers with high molecular weight and cyclic polymers form in the preparation of the ester. Consequently, the viscosity of the reaction mixture in a reactor increases, so that it was difficult to obtain an ester compound in a homogeneous state in a reproducible manner.
Japanese Patent Application Laid-Open 2003-226609 discloses that an ester compound of one or two alcohols with dimer acid, or an ester compound of at least three alcohols with dimer acid is used as an oily base. There, use is made of higher alcohol, such as behenyl alcohol, stearyl alcohol, isostearyl alcohol, phytosterol. These ester compounds are called a wax type and their affinity to skin is weak.
Japanese Patent Application Laid-Open 2003-238332 discloses a cosmetic comprising an oligomer with a number average molecular weight of from 2,000 to 8,000 obtained by reaction of dimer acid with hardened castor oil. However, the oligomer is poor in compatibility with oily bases.
All of the ester compounds described in the afore-mentioned specifications are poor in compatibility or miscibility with various cosmetics and oily bases, so that their amounts in cosmetics are inevitably limited. Therefore, it was difficult to obtain cosmetics with good practical properties such as affinity, emollient property, and oily feeling.
Japanese Patent Application Laid-Open 2004-256515 discloses an oily base comprising (a) an ester obtained by esterification of an oligomeric ester of dimer acid and a di- or higher-valent alcohol with a monovalent alcohol and/or a monovalent carboxylic acid, or (b) an ester obtained by esterification of an oligomeric ester of dimer diol and a di- or higher-valent carboxylic acid with a monovalent alcohol and/or a monovalent carboxylic acid.
Processes for the preparation of ester (a) are disclosed wherein dimer acid is reacted with di- or higher-valent alcohol so as to obtain an oligomeric ester, and then the carboxyl groups and/or the hydroxyl groups of the oligomeric ester are esterified with a monovalent alcohol and/or monovalent carboxylic acid, or wherein dimer acid, di- or higher-valent alcohol, and a monovalent alcohol and/or a monovalent carboxylic acid are reacted at once for esterification. Processes for the preparation of ester (b) are disclosed wherein a dimer diol is reacted with a di- or higher-valent carboxylic acid so as to obtain an oligomeric ester, and then carboxylic groups and/or hydroxyl groups of the oligomeric ester are esterified with a monovalent alcohol and/or a carboxylic acid, or wherein a dimer diol, a di- or higher-valent carboxylic acid, and a monovalent alcohol and/or a monovalent carboxylic acid are reacted at once for esterfication.
In Examples 7 and 8, ester (a) was prepared by reacting an oligomeric ester from dimer acid with 1,10-decane diol or diethylene glycol, and then esterifying the oligomeric ester with a mixture of alcohol (behenyl alcohol and phytosterol). Ester (b) was prepared in Examples 1 to 5 and Example 9 by preparing an oligomeric ester from dimer acid and dimer diol, and then esterifying the oligomeric ester with isostearyl alcohol, behenyl alcohol, isostearic acid, or a mixture of alcohols (behenyl alcohol, isostearyl alcohol and phytosterol) and, in Example 6, by reacting dimer acid, dimer diol, and a mixture of alcohols at once for esterification. For ester (b), dimer diol was used as a raw material instead of di- or higher-valent alcohol.
The viscosities at 60 degrees C. of these esters range from 250 to 4,200 mPa·s, the weight average molecular weights range from 3,300 to 14,800, and the hydroxyl values range form 3.4 to 18.1 (Examples 1 to 9). Above all, the hydroxyl values are very low, so that the esters have drawbacks such as a poor moisturizing property and a poor emollient property.
Japanese Patent Application Laid-Open 2005-132729 discloses cosmetics comprising a mixed ester of aliphatic acids obtained by esterification of polyglycerin, dimer acid, and saturated aliphatic acid and/or unsaturated aliphatic acid. In Examples 1 and 2, diglycerin, dimer acid and carboxylic acid are placed in a reactor at once for esterfication. There, the molar ratios among diglycerin, carboxylic acid and dimer acid are 1.0:2.74:0.51 and 1.0:2.22:1.02, respectively. The hydroxyl value, the viscosity at 60 degrees C., and the number average molecular weight of the obtained mixed ester of aliphatic acids are 5, 1,200 mPa·s, and 1,800 in Example 1 and 2.5, 7,200 mPa·s, and 5,500 in Example 2.
The hydroxyl values of the esters thus obtained are very low, as seen for the above-described esters.